1. Field of the Invention
The present invention relates generally to crushers for rocks, ores, and the like, and more particularly to a crusher having opposed crushing jaws which are driven by resonantly-excited beams.
2. Description of the Prior Art
Crushing raw materials to reduce them to a smaller size is a process basic to many industries. Such crushing typically takes place in several stages with large pieces of, for example, mineral ore being fed first to a jaw-type crusher which breaks the ore down into pieces which are several inches across. Such crushers typically include a reciprocable jaw adjacent a fixed wall. Either the surface of the jaw, the wall, or both, is inclined so that the jaw and the wall define a chamber having a decreasing width in the downward direction. By feeding the ore to the chamber and by driving the jaw periodically inward against the wall, the ore is broken down into successively smaller pieces as it moves downward. Once the ore has been broken into pieces corresponding to the maximum distance between the lower ends of the jaw and the wall, it falls to a receptacle or conveyer for further processing. Crushers of this type normally operate continuously with the larger pieces being fed on top urging those pieces below downward so that they will be crushed.
Upon discharge from the jaw-type crusher, the ore may be fed to a cone crusher for further size reduction. The cone crusher discharges material a fraction of an inch across. This material may then be fed to a ball (or rod) mill to produce a fine, particulate material in a broad range of mesh sizes.
It is thus desirable to provide a jaw-type crusher which would reduce the material size sufficiently so that additional stages of crushing would no longer be necessary to produce a broad range of material sizes.
Typically, jaw-type crushers have been powered by mechanical means which apply force directly between the jaw and the frame of the crusher. While such a construction has proven workable, it suffers from severe maintenance problems resulting from the stress placed on the frame. It is thus desireable to provide a crusher where the crushing jaw is powered by means which impart little or no force to the frame of the crusher.
In order to reduce vibrations, attempts have been made to power jaw-type crushers using horizontally-mounted beams to drive a pair of crushing jaws mounted to receive feed material therebetween. See, for example, U.S. Pat. Nos. 3,131,878; 3,284,010; and 3,414,203. In each of these, a standing, longitudinal wave is induced in the beams to cause the jaws to reciprocate relative to each other. In order to function properly, such machines require very long beams which greatly increase the cost of constructing the machine. If the beams are shortened, the crusher operates at high frequency and low amplitude, characteristics which are not effective in most crushing operations.
It is known to reciprocally drive devices by placing them at an anti-node of a member which is vibrating transversely at or near its resonant frequency. See, for example, U.S. Pat. Nos. 3,232,669 and 3,367,716 to Bodine, which disclose the theoretical advantages in using such resonant systems to apply large forces. It is unknown, however, to combine such transverse resonant drive means in opposed relation in a crusher for rocks, ores and the like to achieve the objects of the present invention as set forth above.